In recent years, due to changes in market prices of coal, the quality of coal for thermal power plant boiler burning is not only significantly poorer than the designed coal quality, but also the coal quality changes frequently, resulting in the varying of boiler coal consumption at the same load, thereby causing the seriously insufficient output of a pulverizing system, so that the fineness of coal powders is coarse, seriously affecting the operation safety and economy of the power station pulverized coal boiler. In order to increase the output of the pulverizing system and reduce the unit consumption of pulverization of a steel-ball coal mill, a variety of coal powders sorting techniques are introduced. In the variety of coal powders sorting techniques, a tandem biaxial coarse powder separator is vigorously promoted in practical applications due to its low resistance and high separation efficiency. However, it also has the problems of serious wear and being easy to deposit powders on the baffles, etc. With the constantly improving of dynamic separation techniques, the dynamic separator is widely used in medium speed coal mills because it has the advantages of large coal fineness adjustable range and high coal powder uniformity index etc., and at the same time, the dynamic separation techniques also begin to be used in an intermediate storage pulverizing system of the steel-ball coal mill. However, when the quality of the milled coal becomes worse, the dynamic separator also has problems of the fineness of the coal powders being finer, increasing the circulation rate, reducing the separation efficiency, and increasing the resistance, thereby limiting the development of dynamic separation techniques.